This invention relates generally to a method of determining the remaining life of an electrochemical cell and, more particularly, to a cell having an operating voltage which is essentially independent of the remaining life of the cell.
Electrochemical cells having the feature noted above have made the design of load circuits less complicated because of a constant output voltage, but a remaining concern is the amount of life remaining at any particular time. Some have avoided to an extent this concern by overdesigning the battery itself so that it would "certainly" last for its intended use especially if the battery is used in a one-shot condition, for example, the launching of a missile held in storage. This design may be an answer to this unique situation, but the question of remaining battery life remains unanswered. Others have designed such batteries so that an indication of pending failure is noted by an abrupt change in output voltage so that replacement occurs without interruption of service. Further, deterioration of the active materials, anode, cathode, and electrolyte, also decreases the life of a battery even before use.
A method to determine the remaining battery life is needed so that batteries are not overdesigned or specially designed thus costing much more to indicate such a condition.